面向星载MIMO-SAR同频干扰抑制的多维正交信号技术研究

Recently, a novel conception of Synthetic Aperture Radar (SAR) based on Multi-Input Multi-Output (MIMO) technology is proposed for its potential advantages in the application of High-Resolution Wide-Swath (HRWS) imaging and simultaneously multimodal imaging. However, performances of such systems are seriously limited by the shared spectrum interference introduced. Traditional orthogonal signals cannot suppress the interference because of the energy conservation constraint. Multi-dimensional orthogonal signal, which is jointly modulated in multiple dimensions such as time, space, frequency and Doppler, can suppress the shared spectrum interference to 38dB. It has supported the development of the first airborne MIMO-SAR system in the world. But the existing multidimensional waveform schemes are not suitable for spaceborne platforms. Consequently, this project aims to research on the multidimensional orthogonal waveforms for spaceborne MIMO-SAR shared spectrum interference suppression. Firstly, the drawbacks of traditional imaging orthogonal waveforms are analyzed from the perspective of ambiguity function and energy conservation, along with the established theoretical basis for the shared spectrum interference suppression effectiveness of multidimensional orthogonal signals. Secondly, a practical multidimensional orthogonal waveform scheme for the suppression of spaceborne MIMO-SAR shared spectrum interference is designed and evaluated by mining the multidimensional Degree Of Freedom (DOF) in frequency domain, space-time domain and Doppler domain et al. Through the above research, simultaneously multimode imaging for spaceborne SAR, such as high resolution, wide swath, polarametric and interferometric can be realized in the near future.

多输入多输出合成孔径雷达（MIMO-SAR）是近年提出的一种新体制雷达，可解决常规SAR面临的高分辨率与宽测绘带矛盾及同时多模式成像等问题。但该雷达性能严重制约于多路信号间的同频干扰。传统正交信号受能量守恒约束，没有同频干扰抑制能力。多维正交信号作为一种具备多维联合调制特征的广义波形，可实现38dB的同频干扰抑制比，且已支撑研制了国际首部机载MIMO-SAR系统。但现有多维波形方案不适用星载平台。本项目拟在机载MIMO-SAR基础上开展面向星载MIMO-SAR同频干扰抑制的多维正交信号技术研究。首先从模糊函数、能量守恒等角度分析传统正交信号限制，并建立多维正交信号可有效抑制同频干扰的理论依据；其次，挖掘频率、时空和多普勒等维度内的自由度，设计适用于星载MIMO-SAR同频干扰抑制的多维正交信号方案，并开展效能评估，最终为星载高分辨率、宽测绘带、全极化干涉等多模式同时工作奠定基础。

该项目在机载MIMO-SAR系统研制经验基础上开展了面向星载MIMO-SAR同频干扰抑制的多维正交信号技术研究，解决了星载构型下的MIMO-SAR同频干扰抑制难题。项目的主要贡献包括：从模糊函数、能量守恒等角度分析了传统正交信号限制，建立了多维正交信号可有效抑制同频干扰的理论依据；设计了适用于星载MIMO-SAR同频干扰抑制的多维正交信号方案，并完成了效能评估，为星载高分辨率、宽测绘带、全极化干涉等多模式同时工作奠定基础。